Super Fly: The Unexpected Lives of the World's Most Successful Insects

by Jonathan Balcombe

Many bat flies cannot fly, and some are wingless. After all, why bother flying when your winged hosts can do the flying for you. These weird insects can be identified as flies only after detailed examination, as Steve Marshall explains: “Males and newly emerged females are normal-looking fully winged bat parasites, but [a few] females undergo extraordinary transformations once they find their hosts. Upon arrival on an appropriate host the female burrows almost entirely under the bat’s skin, loses her wings and legs, and undergoes extensive bloating of the abdomen so that it envelops the head and thorax. Once encysted under the bat’s skin, the female fly becomes little more than a bloodsucking bag that contains a developing larva; it is hardly recognizable as an insect, let alone a fly.”